docs: def save_to(self, nameprefix, switch=False):
          """saves logger data to a different set of files, for
          ``switch=True`` also the loggers name prefix is switched to
          the new value
  
          """
          if not nameprefix or not isinstance(nameprefix, basestring):
              raise _Error('filename prefix must be a nonempty string')
  
          if nameprefix == self.default_prefix:
              raise _Error('cannot save to default name "' + nameprefix + '...", chose another name')
  
          if nameprefix == self.name_prefix:
              return
  
          for name in self.file_names:
              open(nameprefix + name + '.dat', 'w').write(open(self.name_prefix + name + '.dat').read())
  
          if switch:
              self.name_prefix = nameprefix